arXiv subjects

Marco Scodeggio

Publications and source records attributed to Marco Scodeggio.

At least 19 recordsLinked to original sources

arXiv2026

A SHARP Look at Quenching and Bulge-Disk Growth in Massive Galaxies at Cosmic Noon

The physical mechanisms that quench star formation in massive galaxies remain poorly understood. At cosmic noon (1 3x sharper than JWST) and broad near-IR wavelength coverage with 12-IFU multiplexing. This will enable, for the first time, a simultaneous bulge-disk decomposition of stellar populations and spatially resolved mapping of ionised gas in massive galaxies (log $M_*/M_{\odot}\geq 11$) at 2.2 15-20 per spectral resolution element, on the inner bulge, and outer disk extracted spectral continuum, and S/N>5 for nebular lines ([OII], H$\beta$, [OIII], H$\alpha$) on sub-kpc scales. These observations will allow us to reconstruct independent bulge and disk star-formation histories, ages, metallicities, and $\alpha$-enhancements, while mapping spatially resolved star formation, gas kinematics, and feedback-driven outflows. By directly comparing the timing of bulge growth and star-formation suppression across galaxy components, this programme will test whether quenching proceeds inside-out, distinguish fast and slow quenching pathways, and link structural transformation to feedback processes in the most massive galaxies at cosmic noon.

astro-ph.GA↗

arXiv2026

WST -- Wide-field Spectroscopic Telescope: The Next Leap in Wide-field Spectroscopy

The Wide-field Spectroscopic Telescope (WST) is a concept for a dedicated 12-m spectroscopic survey facility designed to address some of the most important questions in astrophysics in the 2040s. The WST will provide unprecedented spectroscopic survey capabilities by operating simultaneously over a 2-degree diameter field of view with 54 low-resolution spectrographs fed by 30,000 fibres, 8-16 high-resolution spectrographs fed by 2,000 fibres, and a large panoramic low-resolution integral-field spectrograph. Supported by Horizon Europe, the concept study has refined the science cases, facility architecture, operations model, sustainability strategy, and technology roadmap. The resulting reference design demonstrates that the WST is both scientifically transformative and technically feasible, while identifying the developments required to mitigate the remaining risks. The WST is designed as an ESO flagship facility for the post-ELT construction era and a key spectroscopic complement to the major imaging, time-domain, and multi-messenger facilities of the coming decades.

astro-ph.IM↗

arXiv2022

SIPGI: an interactive pipeline for spectroscopic data reduction

SIPGI is a spectroscopic pipeline for the data reduction of optical/near-infrared data acquired by slit-based spectrographs. SIPGI is a complete spectroscopic data reduction environment retaining the high level of flexibility and accuracy typical of the standard "by-hand" reduction methods but with a significantly higher level of efficiency. This is obtained exploiting three main concepts: 1) a built-in data organiser to classify the data, together with a graphical interface; 2) the instrument model (analytic description of the main calibration relations); 3) the design and flexibility of the reduction recipes: the number of tasks required to perform a complete reduction is minimised, preserving the possibility to verify the accuracy of the main stages of data-reduction process. The current version of SIPGI manages data from the MODS and LUCI spectrographs mounted at the Large Binocular Telescope (LBT) with the idea to extend SIPGI to support other through-slit spectrographs.

astro-ph.IM↗

arXiv2021

A Planck-selected dusty proto-cluster at z=2.16 associated with a strong over-density of massive H$α$ emitting galaxies

We discovered an over-density of H-alpha-emitting galaxies associated with a Planck compact source in the COSMOS field (PHzG237.0+42.5) through narrow-band imaging observations with Subaru/MOIRCS. This Planck-selected dusty proto-cluster at z=2.16 has 38 H-alpha emitters including six spectroscopically confirmed galaxies in the observed MOIRCS 4'x7' field (corresponding to ~2.0x3.5~Mpc^2 in physical scale). We find that massive H-alpha emitters with log(M*/Msun)>10.5 are strongly clustered in the core of the proto-cluster (within ~300-kpc from the density peak of the H-alpha emitters). Most of the H-alpha emitters in this proto-cluster lie along the star-forming main sequence using H-alpha-based SFR estimates, whilst the cluster total SFR derived by integrating the H-alpha-based SFRs is an order of magnitude smaller than those estimated from Planck/Herschel FIR photometry. Our results suggest that H-alpha is a good observable for detecting moderately star-forming galaxies and tracing the large-scale environment in and around high-z dusty proto-clusters, but there is a possibility that a large fraction of star formation could be obscured by dust and undetected in H-alpha observations.

astro-ph.GA↗

arXiv2020

A possible simultaneous fit to the available $e^+e^- \rightarrow \Lambda^+_c \bar{\Lambda}^-_c$ cross section data nearby $\psi(4660)$ by means of a strong correction to the Coulomb enhancement factor

There are two available set of data on the $e^+e^- \rightarrow \Lambda^+_c \bar{\Lambda}_c^-$ cross section above threshold. The BELLE measurement, with ISR return, is compatible with the presence of a resonant state, called $\psi(4660)$ (formerly known as $Y(4660)$), observed also in other final states. The BESIII dataset has shown a different trend, with a flat cross section. We propose a new solution to fit both datasets by means of a strong correction to the Coulomb enhancement factor. Mass and width of the resonant state is extracted.

hep-ph↗

arXiv2018

Growing up in a megalopolis: Environmental effects on galaxy evolution in a supercluster at z~0.65 in UKIDSS UDS

We present a large-scale galaxy structure Cl J021734-0513 at z~0.65 discovered in the UKIDSS UDS field, made of ~20 galaxy groups and clusters, spreading over 10 Mpc. We report on a VLT/VIMOS spectroscopic follow-up program that, combined with past spectroscopy, allowed us to confirm four galaxy clusters (M200 ~ 10^14 Msol) and a dozen associated groups and star-forming galaxy overdensities. Two additional filamentary structures at z ~ 0.62 and z ~ 0.69 and foreground and background clusters at 0.6 < z < 0.7 were also confirmed along the line-of-sight. The structure subcomponents are at different formation stages. The clusters have a core dominated by passive galaxies and an established red sequence. The remaining structures are a mix of star-forming galaxy overdensities and forming groups. The presence of quiescent galaxies in the core of the latter shows that `preprocessing' has already happened before the groups fall into their more massive neighbours. Our spectroscopy allows us to derive spectral index measurements e.g. emission/absorption line equivalent widths, strength of the 4000A break, valuable to investigate the star formation history of structure members. Based on these line measurements, we select a population of `poststarburst' galaxies. These galaxies are preferentially found within the virial radius of clusters, supporting a scenario in which their recent quenching could be prompted by gas stripping by the dense intracluster medium. We derive stellar age estimates using MCMC-based spectral fitting for quiescent galaxies and find a correlation between ages and colours/stellar masses which favours a top-down formation scenario of the red sequence. A catalogue of ~650 redshifts in UDS will be released alongside the paper.

astro-ph.CO↗

arXiv2017

Large-scale retrospective relative spectro-photometric self-calibration in space

We consider the application of relative self-calibration using overlap regions to spectroscopic galaxy surveys that use slit-less spectroscopy. This method is based on that developed for the SDSS by Padmanabhan at al. (2008) in that we consider jointly fitting and marginalising over calibrator brightness, rather than treating these as free parameters. However, we separate the calibration of the detector-to-detector from the full-focal-plane exposure-to-exposure calibration. To demonstrate how the calibration procedure will work, we simulate the procedure for a potential implementation of the spectroscopic component of the wide Euclid survey. We study the change of coverage and the determination of relative multiplicative errors in flux measurements for different dithering configurations. We use the new method to study the case where the flat-field across each exposure or detector is measured precisely and only exposure-to-exposure or detector-to-detector variation in the flux error remains. We consider several base dither patterns and find that they strongly influence the ability to calibrate, using this methodology. To enable self-calibration, it is important that the survey strategy connects different observations with at least a minimum amount of overlap, and we propose an "S"-pattern for dithering that fulfills this requirement. The final survey strategy adopted by Euclid will have to optimise for a number of different science goals and requirements. The large-scale calibration of the spectroscopic galaxy survey is clearly cosmologically crucial, but is not the only one.

astro-ph.IM↗

arXiv2014

CLASH-VLT: Constraints on the Dark Matter Equation of State from Accurate Measurements of Galaxy Cluster Mass Profiles

A pressureless scenario for the Dark Matter (DM) fluid is a widely adopted hypothesis, despite the absence of a direct observational evidence. According to general relativity, the total mass-energy content of a system shapes the gravitational potential well, but different test particles perceive this potential in different ways depending on their properties. Cluster galaxy velocities, being $\ll$c, depend solely on the gravitational potential, whereas photon trajectories reflect the contributions from the gravitational potential plus a relativistic-pressure term that depends on the cluster mass. We exploit this phenomenon to constrain the Equation of State (EoS) parameter of the fluid, primarily DM, contained in galaxy clusters. We use the complementary information provided by the kinematic and lensing mass profiles of the galaxy cluster MACS 1206.2-0847 at $z=0.44$, as obtained in an extensive imaging and spectroscopic campaign within the CLASH survey. The unprecedented high quality of our data-set and the properties of this cluster are well suited to determine the EoS parameter of the cluster fluid. Since baryons contribute at most $15\%$ to the total mass in clusters and their pressure is negligible, the EoS parameter we derive describes the behavior of the DM fluid. We obtain the most stringent constraint on the DM EoS parameter to date, $w=(p_r+2\,p_t)/(3\,c^2ρ)=0.00\pm0.15\mathrm{(stat)}\pm0.08\mathrm{(syst)}$, averaged over the radial range $0.5\,\mathrm{Mpc}\leq$$r$$\leq$$r_{200}$, where $p_r$ and $p_t$ are the radial and tangential pressure, and $ρ$ is the density. We plan to further improve our constraint by applying the same procedure to all clusters from the ongoing CLASH-VLT program.

astro-ph.CO↗

arXiv2013

The Contribution of Halos with Different Mass Ratios to the Overall Growth of Cluster-Sized Halos

We provide a new observational test for a key prediction of the ΛCDM cosmological model: the contributions of mergers with different halo-to-main-cluster mass ratios to cluster-sized halo growth. We perform this test by dynamically analyzing seven galaxy clusters, spanning the redshift range $0.13 < z_c < 0.45$ and caustic mass range $0.4-1.5$ $10^{15} h_{0.73}^{-1}$ M$_{\odot}$, with an average of 293 spectroscopically-confirmed bound galaxies to each cluster. The large radial coverage (a few virial radii), which covers the whole infall region, with a high number of spectroscopically identified galaxies enables this new study. For each cluster, we identify bound galaxies. Out of these galaxies, we identify infalling and accreted halos and estimate their masses and their dynamical states. Using the estimated masses, we derive the contribution of different mass ratios to cluster-sized halo growth. For mass ratios between ~0.2 and ~0.7, we find a ~1 $σ$ agreement with ΛCDM expectations based on the Millennium simulations I and II. At low mass ratios, $\lesssim 0.2$, our derived contribution is underestimated since the detection efficiency decreases at low masses, $\sim 2 \times 10^{14}$ $h_{0.73}^{-1}$ M$_{\odot}$. At large mass ratios, $\gtrsim 0.7$, we do not detect halos probably because our sample, which was chosen to be quite X-ray relaxed, is biased against large mass ratios. Therefore, at large mass ratios, the derived contribution is also underestimated.

astro-ph.CO↗

arXiv2013

Galaxy halo truncation and Giant Arc Surface Brightness Reconstruction in the Cluster MACSJ1206.2-0847

In this work we analyze the mass distribution of MACSJ1206.2-0847, especially focusing on the halo properties of its cluster members. The cluster appears relaxed in its X-ray emission, but has significant amounts of intracluster light which is not centrally concentrated, suggesting that galaxy-scale interactions are still ongoing despite the overall relaxed state. The cluster lenses 12 background galaxies into multiple images and one galaxy at $z=1.033$ into a giant arc and its counterimage. The multiple image positions and the surface brightness distribution (SFB) of the arc which is bent around several cluster members are sensitive to the cluster galaxy halo properties. We model the cluster mass distribution with a NFW profile and the galaxy halos with two parameters for the mass normalization and extent of a reference halo assuming scalings with their observed NIR--light. We match the multiple image positions at an r.m.s. level of $0.85\arcsec$ and can reconstruct the SFB distribution of the arc in several filters to a remarkable accuracy based on this cluster model. The length scale where the enclosed galaxy halo mass is best constrained is about 5 effective radii -- a scale in between those accessible to dynamical and field strong lensing mass estimates on one hand and galaxy--galaxy weak lensing results on the other hand. The velocity dispersion and halo size of a galaxy with $m_{\rm 160W,AB}=19.2$ or $M_{\rm B,Vega}=-20.7$ are $σ=150 \rm kms^{-1}$ and $r\approx 26\pm 6 \rm kpc$, indicating that the halos of the cluster galaxies are tidally stripped. We also reconstruct the unlensed source (which is smaller by a factor of $\sim5.8$ in area), demonstrating the increase of morphological information due to lensing and conclude that this galaxy has likely star--forming spiral arms with a red (older) central component.

astro-ph.CO↗

arXiv2013

F-VIPGI: a new adapted version of VIPGI for FORS2 spectroscopy. Application to a sample of 16 X-ray selected galaxy clusters at 0.6 < z < 1.2

The goal of this paper is twofold. Firstly, we present F-VIPGI, a new version of the VIMOS Interactive Pipeline and Graphical Interface (VIPGI) adapted to handle FORS2 spectroscopic data. Secondly, we investigate the spectro-photometric properties of a sample of galaxies residing in distant X-ray selected galaxy clusters, the optical spectra of which were reduced with this new pipeline. We provide basic technical information about the innovations of the new software and, as a demonstration of the capabilities of the new pipeline, we show results obtained for 16 distant (0.65 < z < 1.25) X-ray luminous galaxy clusters selected within the XMM-Newton Distant Cluster Project. We performed a spectral indices analysis of the extracted optical spectra of their members, based on which we created a library of composite high signal-to-noise ratio spectra representative of passive and star-forming galaxies residing in distant galaxy clusters. The spectroscopic templates are provided to the community in electronic form. By comparing the spectro-photometric properties of our templates with the local and distant galaxy population residing in different environments, we find that passive galaxies in clusters appear to be well evolved already at z = 0.8 and even more so than the field galaxies at similar redshift. Even though these findings would point toward a significant acceleration of galaxy evolution in densest environments, we cannot exclude the importance of the mass as the main evolutionary driving element either. The latter effect may indeed be justified by the similarity of our composite passive spectrum with the luminous red galaxies template at intermediate redshift.

astro-ph.IM↗

arXiv2012

CLASH: Mass Distribution in and around MACS J1206.2-0847 from a Full Cluster Lensing Analysis

We derive an accurate mass distribution of the galaxy cluster MACS J1206.2-0847 (z=0.439) from a combined weak-lensing distortion, magnification, and strong-lensing analysis of wide-field Subaru BVRIz' imaging and our recent 16-band Hubble Space Telescope observations taken as part of the Cluster Lensing And Supernova survey with Hubble (CLASH) program. We find good agreement in the regions of overlap between several weak and strong lensing mass reconstructions using a wide variety of modeling methods, ensuring consistency. The Subaru data reveal the presence of a surrounding large scale structure with the major axis running approximately north-west south-east (NW-SE), aligned with the cluster and its brightest galaxy shapes, showing elongation with a \sim 2:1 axis ratio in the plane of the sky. Our full-lensing mass profile exhibits a shallow profile slope dlnΣ/dlnR\sim -1 at cluster outskirts (R>1Mpc/h), whereas the mass distribution excluding the NW-SE excess regions steepens further out, well described by the Navarro-Frenk-White form. Assuming a spherical halo, we obtain a virial mass M_{vir}=(1.1\pm 0.2\pm 0.1)\times 10^{15} M_{sun}/h and a halo concentration c_{vir} = 6.9\pm 1.0\pm 1.2 (\sim 5.7 when the central 50kpc/h is excluded), which falls in the range 4< <7 of average c(M,z) predictions for relaxed clusters from recent Lambda cold dark matter simulations. Our full lensing results are found to be in agreement with X-ray mass measurements where the data overlap, and when combined with Chandra gas mass measurements, yield a cumulative gas mass fraction of 13.7^{+4.5}_{-3.0}% at 0.7Mpc/h (\approx 1.7r_{2500}), a typical value observed for high mass clusters.

astro-ph.CO↗

arXiv2010

The bulk of the black hole growth since z~1 occurs in a secular universe: No major merger-AGN connection

What is the relevance of major mergers and interactions as triggering mechanisms for active galactic nuclei (AGN) activity? To answer this longstanding question, we analyze 140 XMM-selected AGN host galaxies and a matched control sample of 1264 inactive galaxies over z~0.3-1.0 and log(M_*/M_sun)<11.7 with high-resolution HST/ACS imaging from the COSMOS field. The visual analysis of their morphologies by 10 independent human classifiers yields a measure of the fraction of distorted morphologies in the AGN and control samples, i.e. quantifying the signature of recent mergers which might potentially be responsible for fueling/triggering the AGN. We find that (1) the vast majority (>85%) of the AGN host galaxies do not show strong distortions, and (2) there is no significant difference in the distortion fractions between active and inactive galaxies. Our findings provide the best direct evidence that, since z~1, the bulk of black hole accretion has not been triggered by major galaxy mergers, therefore arguing that the alternative mechanisms, i.e., secular processes and minor interactions, are the leading triggers for the episodes of major black hole growth. We also exclude an alternative interpretation of our results: a significant time lag between merging and the observability of the AGN phase could wash out the most significant merging signatures, explaining the lack of enhancement of strong distortions on the AGN hosts. We show that this alternative scenario is unlikely due to: (1) recent major mergers being ruled out for the majority of sources due to the high fraction of disk-hosted AGN, (2) the lack of a significant X-ray signal in merging inactive galaxies as a signature of a potential buried AGN, and (3) the low levels of soft X-ray obscuration for AGN hosted by interacting galaxies, in contrast to model predictions.

astro-ph.CO↗

arXiv2002

Spectro-photometry of galaxies in the Virgo cluster

As a result of an extensive observational campaign targeting the Virgo cluster, we obtained integrated (drift-scan mode) optical spectra and multiwavelength (UV,U,B,V,H) photometry for 124 and 330 galaxies, respectively, spanning the whole Hubble sequence, and with m_p<=16 (M_p<=-15). These data were combined to obtain galaxy SEDs extending from 2000 to 22000 A. By fitting these SEDs with synthetic ones derived using Bruzual & Charlot population synthesis models we try to constrain observationally the SFH of these galaxies. Assuming a Salpeter IMF and an analytical form for the SFH, the fit free parameters are: the age (T) of the star formation event, its characteristic time-scale (tau) and the initial metallicity (Z). We test the (simplistic) case where all galaxies have a common age T=13 Gyr, exploring a SFH with "delayed" exponential form, thus allowing for an increasing SFR with time. This SFH is consistent with the full range of observed SEDs, provided that the characteristic time-scale tau is let free to vary between 0.1 and 25 Gyr and Z between 1/5 and 2.5 Z solar. Elliptical galaxies (including dEs) are best fitted with short time scales (tau~3 Gyr) and Z varying between 1/5 and 1 Z solar. The model metallicity is found to increase with H band luminosity. Spiral galaxies require that both tau and Z correlate with H band luminosity: low mass Im+BCD have sub-solar Z and tau>=10 Gyr, whereas giant spirals have solar metallicities and tau~3 Gyr, consistent with ellipticals. Moreover we find that the SFH of spirals depends upon the presence at their interior of fresh gas capable of sustaining the star formation. In fact the residuals of the tau vs. L_H relation depend significantly on the HI content. HI deficient galaxies have shorter tau than spirals with normal HI content.

astro-ph↗

arXiv2001

Internal color gradients and the color-magnitude relation of early-type galaxies

The traditional use of fixed apertures in determining the well known color-magnitude (CM) relation of early type galaxies, coupled with the presence of radial color gradients within these systems, introduces a bias in the CM relation itself. The effect of this bias is studied here deriving a CM relation which is based on color measurements carried out homogeneously within an aperture of radius equal to that of the galaxy effective radius. A sample of 48 giant early-type galaxies in the Coma cluster, with CCD observations in the U- and V-band, is used for this derivation. It is found that internal radial color gradients in early-type galaxies cannot be neglected when discussing the colors of these systems, and that the CM relation derived using color measurements within the effective radius is significantly flatter than those based on fixed-aperture color measurements. With the presently available data it is impossible to determine whether the relation is completely flat, or whether a small correlation is still present between galaxy color and luminosity.

astro-ph↗

arXiv2000

1.65mic (H-band) surface photometry of galaxies. VI: The history of star formation in normal late-type galaxies

We have collected a large body of NIR (H band), UV (2000 A) and Halpha measurements of late-type galaxies. These are used, jointly with spectral evolutionary synthesis models, to study the initial mass function (IMF) in the mass range m > 2 Mo. For spirals (Sa-Sd), Magellanic irregulars (Im) and blue compact dwarfs (BCD), our determination is consistent with a Salpeter IMF with an upper mass cutoff M_up = 80 Mo. The history of star formation and the amount of total gas (per unit mass) of galaxies are found to depend primarily on their total masses (as traced by the H band luminosities) and only secondarily on morphological type. The present star formation activity of massive spirals is up to 100 times smaller than that average over their lifetime, while in low mass galaxies it is comparable to or higher than that at earlier epochs. Dwarf galaxies have presently larger gas reservoirs per unit mass than massive spirals. The efficiency in transforming gas into stars and the time scale for gas depletion (10 Gyrs) are independent of the luminosity and/or of the morphological type. These evidences are consistent with the idea that galaxies are coeval systems,that they evolved as closed-boxes forming stars following a simple, universal star formation law whose characteristic time scale is small (1 Gyr) in massive spirals and large (10 Gyr) in low mass galaxies. A similar conclusion was drawn by Gavazzi and Scodeggio (1996) to explain the colour-magnitude relation of late-type galaxies. The consequences of this interpretation on the evolution of the star formation rate and of the gas density per comoving volume of the Universe with look-back time are discussed.

astro-ph↗

arXiv2000

The late afterglow and host galaxy of GRB 990712

We present deep HST imaging, as well as ground-based imaging and spectroscopy, of the optical afterglow associated with the long-duration gamma-ray burst GRB 990712 and its host galaxy. The data were obtained 48--123 days after the burst occurred. The magnitudes of the host (R = 21.9, V = 22.5) and optical afterglow (R = 25.4, V = 25.8, 47.7 days after the burst) favor a scenario where the optical light follows a pure power-law decay with an index of alpha ~ -1.0. We find no evidence for a contribution from a supernova like SN1998bw. This suggests that either there are multiple classes of long-duration gamma-ray bursts, or that the peak luminosity of the supernova was > 1.5 mag fainter than SN1998bw. The HST images and EFOSC2 spectra indicate that the gamma-ray burst was located in a bright, extended feature (possibly a star-forming region) 1.4 kpc from the nucleus of a 0.2 L^*_B galaxy at z = 0.434, possibly a Seyfert 2 galaxy. The late-time afterglow and host galaxy of GRB 990712 bear some resemblance to those of GRB 970508.

astro-ph↗

arXiv1997

Seeking the Local Convergence Depth. II. TF Observations of the Clusters A114, A119, A194, A2295, A2457, A2806, A3193, A3381, AND A3744

We present Tully-Fisher (TF) observations for nine rich Abell clusters of galaxies. This is the second such data installment of an all-sky survey of 50 clusters in the redshift range 0.02 < z < 0.06. The data extends the TF study of nearby clusters of Giovanelli et al.; they will be used jointly to determine an accurate I band TF template and to establish a cluster inertial reference frame to z = 0.06.

astro-ph↗